package com.qianke.common.util;

import java.security.MessageDigest;
import java.text.SimpleDateFormat;
import java.util.Date;

public class MD5 {
    /**
     * 单例
     */
    private static MD5 instance;

    /**
     * 四个链接变量
     */
    private static final int A = 0x67452301;
    private static final int B = 0xefcdab89;
    private static final int C = 0x98badcfe;
    private static final int D = 0x10325476;

    /**
     * ABCD的临时变量
     */
    private static int Atemp;
    private static int Btemp;
    private static int Ctemp;
    private static int Dtemp;

    /**
     * 常量ti
     * 公式:floor(abs(sin(i+1))×(2pow32)
     */
    private static final int[] K = {
            0xd76aa478, 0xe8c7b756, 0x242070db, 0xc1bdceee,
            0xf57c0faf, 0x4787c62a, 0xa8304613, 0xfd469501, 0x698098d8,
            0x8b44f7af, 0xffff5bb1, 0x895cd7be, 0x6b901122, 0xfd987193,
            0xa679438e, 0x49b40821, 0xf61e2562, 0xc040b340, 0x265e5a51,
            0xe9b6c7aa, 0xd62f105d, 0x02441453, 0xd8a1e681, 0xe7d3fbc8,
            0x21e1cde6, 0xc33707d6, 0xf4d50d87, 0x455a14ed, 0xa9e3e905,
            0xfcefa3f8, 0x676f02d9, 0x8d2a4c8a, 0xfffa3942, 0x8771f681,
            0x6d9d6122, 0xfde5380c, 0xa4beea44, 0x4bdecfa9, 0xf6bb4b60,
            0xbebfbc70, 0x289b7ec6, 0xeaa127fa, 0xd4ef3085, 0x04881d05,
            0xd9d4d039, 0xe6db99e5, 0x1fa27cf8, 0xc4ac5665, 0xf4292244,
            0x432aff97, 0xab9423a7, 0xfc93a039, 0x655b59c3, 0x8f0ccc92,
            0xffeff47d, 0x85845dd1, 0x6fa87e4f, 0xfe2ce6e0, 0xa3014314,
            0x4e0811a1, 0xf7537e82, 0xbd3af235, 0x2ad7d2bb, 0xeb86d391
    };

    /**
     * 向左位移数,计算方法未知
     */
    private static final int[] s = {
            7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22, 7,
            12, 17, 22, 5, 9, 14, 20, 5, 9, 14, 20, 5, 9, 14, 20, 5, 9, 14, 20,
            4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23, 6, 10,
            15, 21, 6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15, 21
    };

    /**
     * 私有构造函数
     */
    private MD5() {

    }

    /**
     * 单例模式
     *
     * @return
     */
    public static MD5 getInstance() {
        if (instance == null) {
            instance = new MD5();
        }
        return instance;
    }

    /**
     * 初始化函数
     */
    private static void init() {
        Atemp = A;
        Btemp = B;
        Ctemp = C;
        Dtemp = D;
    }

    /**
     * 移动一定位数
     *
     * @param a
     * @param s
     * @return
     */
    private static int shift(int a, int s) {
        return (a << s) | (a >>> (32 - s)); // 右移的时候，高位一定要补零，而不是补充符号位
    }

    /**
     * 主循环
     *
     * @param M
     */
    private static void mainLoop(int[] M) {
        int F;
        int g;
        int a = Atemp;
        int b = Btemp;
        int c = Ctemp;
        int d = Dtemp;

        for (int i = 0; i < 64; i++) {
            if (i < 16) {
                F = (b & c) | ((~b) & d);
                g = i;
            } else if (i < 32) {
                F = (d & b) | ((~d) & c);
                g = (5 * i + 1) % 16;
            } else if (i < 48) {
                F = b ^ c ^ d;
                g = (3 * i + 5) % 16;
            } else {
                F = c ^ (b | (~d));
                g = (7 * i) % 16;
            }

            int tmp = d;
            d = c;
            c = b;
            b = b + shift(a + F + K[i] + M[g], s[i]);
            a = tmp;
        }

        Atemp += a;
        Btemp += b;
        Ctemp += c;
        Dtemp += d;
    }

    /**
     * 填充函数
     * 处理后应满足bits≡448(mod512),字节就是bytes≡56（mode64)
     * 填充方式为先加一个0,其它位补零
     * 最后加上64位的原来长度
     *
     * @param str
     * @return
     */
    private static int[] add(String str) {
        int num = ((str.length() + 8) / 64) + 1;    // 以512位，64个字节为一组
        int[] strByte = new int[num * 16];  // 64/4=16，所以有16个整数

        for (int i = 0; i < num * 16; i++) {
            // 全部初始化为0
            strByte[i] = 0;
        }

        int j;
        for (j = 0; j < str.length(); j++) {
            strByte[j >> 2] |= str.charAt(j) << ((j % 4) * 8);  // 一个整数存储四个字节，小端序
        }
        strByte[j >> 2] |= 0x80 << ((j % 4) * 8);   // 尾部添加1

        // 添加原长度，长度指位的长度，所以要乘8，然后是小端序，所以放在倒数第二个,这里长度只用了32位
        strByte[num * 16 - 2] = str.length() * 8;

        return strByte;
    }

    /**
     * 调用函数
     *
     * @param source 原始字符串
     * @return
     */
    public static String encrypt(String source) {
        // 初始化
        init();
        int[] strByte = add(source);
        for (int i = 0; i < strByte.length / 16; i += 16) {
            int[] num = new int[16];
            for (int j = 0; j < 16; j++) {
                num[j] = strByte[i * 16 + j];
            }
            mainLoop(num);
        }
        return changeHex(Atemp) + changeHex(Btemp) + changeHex(Ctemp) + changeHex(Dtemp);
    }

    /**
     * 整数变成16进制字符串
     *
     * @param a 整数
     * @return
     */
    private static String changeHex(int a) {
        String str = "";
        String tmp = "";
        for (int i = 0; i < 4; i++) {
            tmp = Integer.toHexString(((a >> i * 8) % (1 << 8)) & 0xff);
            if (tmp.length() < 2) {
                tmp = "0" + tmp;
            }
            str += tmp;
        }
        return str;
    }


    /**
     * 自定义密码加密 ： password + 账号 + 后缀
     *
     * @param password
     * @return 密文
     */
    public static String encryptPwd(String password, String username, String suff) {
        String pwd = MD5.encrypt(password + username + suff);
        //再加密2次
        pwd = MD5.encrypt(MD5.encrypt(pwd));
        return pwd;
    }


    /**
     * 测试方法
     *
     * @param args
     */
    public static void main(String[] args) {
        //静态加密
        //password + "520it"
        //经过3次加密

        //动态加密
        //password + 账号 + 后缀
        //时间戳
        Date date = new Date();
        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyyMMddHHmmss");
        String newTime = simpleDateFormat.format(date);

        //sig加密
        String sig = "N000000127145fe42640-1d31-11e7-8523-7f187dfae0bf" + newTime;
        System.out.println(MD5.MyMD5(sig));
        //System.out.println(MD5.encrypt(MD5.encrypt(MD5.encrypt("123456520it"))));

    }

    //大写加密
    public final static String MyMD5(String s) {
        char hexDigits[] = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
                'A', 'B', 'C', 'D', 'E', 'F'};
        try {
            byte[] btInput = s.getBytes();
            // 获得MD5摘要算法的 MessageDigest 对象
            MessageDigest mdInst = MessageDigest.getInstance("MD5");
            // 使用指定的字节更新摘要
            mdInst.update(btInput);
            // 获得密文
            byte[] md = mdInst.digest();
            // 把密文转换成十六进制的字符串形式
            int j = md.length;
            char str[] = new char[j * 2];
            int k = 0;
            for (int i = 0; i < j; i++) {
                byte byte0 = md[i];
                str[k++] = hexDigits[byte0 >>> 4 & 0xf];
                str[k++] = hexDigits[byte0 & 0xf];
            }
            return new String(str);
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }


}
